Flare

ABSTRACT

A flare suitable for use for the disposal of combustible waste gases from marine platforms comprises a fuel chamber having tubes passing through it. The interior of the fuel chamber is connected to the bores of the tubes only by Coanda nozzles. During use of the flare, fuel from the fuel chamber passes via the Coanda nozzles into the tubes and thus surrounding air is entrained into the fuel flow. The combustible mixture thus formed is burned off above the tubes.

United States Patent [191 Desty et al.

[ FLARE [75] Inventors: Denis Henry Desty, Weybridge;

Christopher John Young, Horton, both of England The British Petroleum Company [73] Assignee:

Limited, London, England FOREIGN PATENTS OR APPLICATIONS 1,235,302 5/1960 France 239/DIG. 7

Primary Examiner--Edward G. Favors Attorney, Agent, or Firm-Morgan, Finnegan, Durham [22] Filed: May 25, 1973 & Pine [21] Appl. No.: 363,857

. [57] ABSTRACT [30] Foreign Application Priority Data H June 1 1972 Great Britain 25701, A flare suitable for use for the disposal of combustible waste gases from marine platforms comprises a fuel chamber having tubes passing through it. The interior '8 431/328 239m of the fuel chamber is connected to the bores of the [58] Fie'ld 328 174V tubes only by Coanda nozzles. During use of the flare, 3 5 3 fuel from the fuel chamber passes via the Coancla nozzles into the tubes and thus surrounding air is entrained into the fuel flow. The combustible mixture [56] B S;Z S SZ? NTS thus formed is burned off above the tubes. 3,504,994 4/1970, Desty et al. 431/328 x 4 Claims, 4 Drawing Figures L a. I I

I I 8/ I I I a I I 7 9 i J l l [77/ I I I l 1 [J PATENTED DEB] (H974 sum 2 0F 2 FLARE This invention relates to the flaring off of waste combustible gases from marine platforms.

Conventional offshore drilling is usually performed from a platform fixed to the bottom of the ocean or from a floating vessel upon which the drilling apparatus is mounted. The flaring off of waste gases from production units situated on marine platforms presents special problems. In view of the limited space available on the platform the flame arising from the flare must either have low radiation of heat or be shielded so as to protect personnel from radiation, flame lick and high temperature flue gas impingement. A further requirement is that the noise arising from the flaring procedure is not excessive.

Conventional flares are not very suitable on limited marine platform area, the resultant long flames being difficult to shield with the consequent radiation and flame lick hazards.

According to the invention, a burner element of a flare tip suitable for the disposal of waste combustible gases comprises a fuel chamber through which pass a plurality of tubes, there being means for reducing gas velocity attached to the exit of the tubes the interior of the fuel chamber being connected to the bores of the tubes only by means of Coanda nozzles so that, during use of the device, fuel passes from the fuel chamber into the tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, thefuel and air then passing through the tubes exits to a combustion zone.

A Coanda nozzle may be defined as a nozzle capable of discharging a fluid at high pressure into another fluid of low pressure through a narrow slot of chosen dimensions having a curved surface of chosen contour substantially contiguous with one wall of said slot. A suitable form of Coanda nozzle is described in our British Pat. No. 1,278,577.

The shape of the tubes is preferably cylindrical and most preferably the tubes are arranged with their axes parallel to one another.

The means for reducing the gas velocity is preferably a tube of increasing cross-sectional area and is most preferably a diffuser cone projecting above the top plate of the fuel chamber from each tube. The. cone dimensions employed are dependent on the gases flared. Preferably the diffuser cone (a truncated cone) has an included angle'of 3 most preferably 4 6 and the diffuser cone mouth diameter is from one and onehalf to two times its throat diameter.

Preferably the tubes at the Coanda nozzle end have a diameter from 1 inch 3 inches, a separation of centres from 2 inches 6 inches, and a length of 6 inches 12 inches.

It is desirable on grounds of flame stability to have seven or more tubes passing through the fuel chamber, the juxtaposition of the tubes being such asto yield flame stabilisation preferably in the form of a single horizontal flame above the cones. The tubes are preferably in an array and their centres being not greater than five tube diameters apart.

The burner element described above can burn a wide variety of gases e.g., ethane, methane.

Preferably the burner element is of modular construction i.e., the element is made up of a suitable number of small units. This yields advantages in assembly and manufacture of the element. A preferred form of module is triangular in shape. In a preferred construction, a hexagonal burner element having a total of 270 Coanda units.

- The burner element can form part of flares used for burning off waste gases e.g., on a marine platform.

The invention also provides a flare tip suitable for the disposal of combustible gaseous fuel which comprises one or more burner elements as hereinbefore described.

During use of the element in a flare it is preferable to incorporate pilot lights. Preferably, particularly during.

use on a marine platform, radiation and/or wind shields are associated with the burner element.

Further the invention provides a method for the disposal of combustible gaseous fuel whereby the fuel is passed from the fuel chamber of the burner element of a flare tip as hereinbefore described into the tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, the fuel and air then passing through the tube exits to a combustion zone where it is ignited.

The invention will now be described by way of example with reference to the accompanying drawings in which: I

FIG. 1 is a front view of the flarestack mounted on a marine platform.

FIG. 2 is a vertical cross-section of a burner element.

FIG. 3 shows the modular construction of the burner element, and

FIG. 4 shows a plan of an alternative layout.

A flarestack mounted on a marine platform is shown in FIG. 1. The fuel is fed into the flarestack by means of fuel inlet pipe 1 from gas-oil separators and is passed to the burner elements 3 preferably situated away from production units .2. The flarestack is supported by means of a cantilevered support 4 projecting from the marine platform 5. The burner elements 3 are mounted on a tower 6 of height about feet.

A cross-section of the burner element is shown-in FIG. 2. The burner element comprises a fuel chamber 7 through which passes a plurality of tubes 8. The fuel chamber 7 is closed by parallel top and bottom metal plates 9 and 10. The interior of the fuel chamber is connected to the bores of each individual tube 8 by means of Coanda nozzle chamber 14. Bolts secure the fuel chamber, nozzle and tube in position. The tubes 8 protrude some distance above the top plate 9 of the fuel chamber-7 in the form of a diffuser cone 11.

The tubes have a 2% inch diameter at a separation of centres of 4% inch and are 15 inch long. i

In use of the burner element, fuel enters the fuel chamber 7 via the fuel supply line (not shown). The fuel then passes from fuel chamber 7 into the Coanda nozzle' chamber 14 by means of holes 13. The fuel emerges into the tube 8 from the Coanda slot 12. The Coanda effect causes entrainment of surrounding air so that a combustible mixture of fuel gas and air passes along the tube 8 and into the combustion zone which is situated above the diffuser cone 11. The burner construction yields a single horizontal combustion zone spreading over the tubes 8.

FIG. 3 illustrates the modular construction of the burnerelement. The element is made up from six triangular modules 15, eachmodule containing forty five tubes 8. Typically each flare consists of 3 elements, thus the flare contains a total of 3 X 270 810 tubes.

In use, the fuel gas enters the fuel inlet pipe 1. The six triangular modules are surrounded by a common fuel manifold 18. The element or array 3 is mounted around and extending vertically upwards from the burner element.

Each flare consists of three separate hexagonal burners, each about eight feet across the flats mounted horizontally with a wind shield approximately 2 feet high surrounding the burner element. The fuel inlet pipes have a diameter of about 6 inches.

FIG. 4 shows a plan view of the layout indicating the position of the various integers. The main platform 16 is of side 170 feet. The platform is shielded from the burner elements 3 by means of radiation shield 17. The flare is supported from the platform by means of a cantilevered support 4 which also carries the fuel supply to the stack.

We claim:

1. A burner element, comprising: a fuel chamber through which pass a plurality of first tubes, the shape of said first tubes being cylindrical and being arranged with their axes parallel to one another; means for reducing gas velocity comprising second tubes of increasing cross-sectional area attached to the exit of each of said plurality of first tubes; said second tubes of increasing cross-sectional area each comprising a diffuser cone having a throat diameter of 1 inch to 3 inches and a length of 6 inches to 18 inches; the interior of said fuel chamber being connected to the bores of each of said plurality of first tubes only by means of Coanda nozzles so that, in use, fuel passes from said fuel chamher into said first tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, said fuel and air thereafter passing through each of said first tube exits and said second tubes of increasing crosssectional area to a combustion zone to thereby produce a single, self-stabilizing, horizontal flame.

2. A burner element comprising a fuel chamber through which pass a plurality of tubes in an array, the centres of the tubes being not greater than five tube diarneters apart; means for reducing gas velocity attached to the exit of the tubes, the interior of the fuel chamber being connected to the bores of the tubes only by means of Coanda nozzles so that, in use, fuel passes from the fuel chamber into the tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, the fuel and air then passing through the tube exits to a combustion zone to thereby produce a single, self-stabilizing, horizontal flame.

3. A burner element comprising a fuel chamber through which pass a plurality of tubes; means for reducing gas velocity attached to the exit of the tubes, the interior of the fuel chamber being connected to the bores of the tubes only by means of Coanda nozzles so that, in use, fuel passes from the fuel chamber into the tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, the fuel and air then passing through the tube exits to a combustion zone to thereby produce a single, self-stabilizing horizontal flame; said burner element being of modular construction and formed from six triangular modules in the shape of a hexagon.

4. A burner element, comprising; a fuel chamber through which pass a plurality of first tubes, the shape of said first tubes being cylindrical and being arranged with their axes parallel to one another; means for reducing gas velocity comprising second tubes of increasing cross-sectional area attached to the exit of each of said plurality of first tubes; said second tubes of increasing cross-sectional area each comprising a diffuser cone having an included angle of 3l0 and an exit mouth diameter from one and one-half to two times greater than its throat diameter; the interior of said fuel chamber being connected to the bores of each of said plurality of first tubes only by means of Coanda nozzles so that, in use, fuel passes from said fuel chamber into said first tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, said fuel and said air thereafter passing through each of said first tube exits and said second tubes of increasing cross-sectional area to a combustion zone to thereby produce a single, selfstabilizing, horizontal flame. 

1. A burner element, comprising: a fuel chamber through which pass a plurality of first tubes, the shape of said first tubes being cylindrical and being arranged with their axes parallel to one another; means for reducing gas velocity comprising second tubes of increasing cross-sectional area attached to the exit of each of said plurality of first tubes; said second tubes of increasing cross-sectional area each comprising a diffuser cone having a throat diameter of 1 inch to 3 inches and a length of 6 inches to 18 inches; the interior of said fuel chamber being connected to the bores of each of said plurality of first tubes only by means of Coanda nozzles so that, in use, fuel passes from said fuel chamber into said first tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, said fuel and air thereafter passing through each of said first tube exits and said second tubes of increasing cross-sectional area to a combustion zone to thereby produce a single, self-stabilizing, horizontal flame.
 2. A burner element comprising a fuel chamber through which pass a plurality of tubes in an array, the centres of the tubes being not greater than five tube diameters apart; means for reducing gas velocity attached to the exit of the tubes, the interior of the fuel chamber being connected to the bores of the tubes only by means of Coanda nozzles so that, in use, fuel passes from the fuel chamber into the tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, the fuel and air then passing through the tube exits to a combustion zone to thereby produce a single, self-stabilizing, horizontal flame.
 3. A burner element comprising a fuel chamber through which pass a plurality of tubes; means for reducing gas velocity attached to the exit of the tubes, the interior of the fuel chamber being connected to the bores of the tubes only by means of Coanda nozzles so that, in use, fuel passes from the fuel chamber into the tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, the fuel and air then passing through the tube exits to a combustion zone to thereby produce a single, self-stabilizing horizontal flame; said burner element being of modular construction and formed from six triangular modules in the shape of a hexagon.
 4. A burner element, comprising; a fuel chamber through which pass a plurality of first tubes, the shape of said first tubes being cylindrical and being arranged with their axes parallel to one another; means for reducing gas velocity comprising second tubes of increasing cross-sectional area attached to the exit of each of said plurality of first tubes; said second tubes of increasing cross-sectional area each comprising a diffuser cone having an included angle of 3*-10* and an exit mouth diameter from one and one-half to two times greater than its throat diameter; the interior of said fuel chamber being connected to the bores of each of said plurality of first tubes only by means of Coanda nozzles so that, in use, fuel passes from said fuel chamber into said first tubes via the Coanda nozzles thus entraining surrounding air into the fuel flow, said fuel and said air thereafter passing through each of said first tube exits and said second tubes of increasing cross-sectional area to a combustion zone to thereby producE a single, self-stabilizing, horizontal flame. 